The primary functions of the vestibular system are maintaining balance (posture and equilibrium) by monitoring motion of the head, and stabilizing the eyes relative to the environment. There are two components to monitoring motion: detecting angular acceleration (i.e. detecting changes in rotation) and detecting linear acceleration (i.e. detecting changes along a line, such as gravitational changes or changes in forward motion). Secondary functions of the vestibular system are to provide critical information for sensory system integration. Sensory integration is the ability of the central nervous system to gather current information such as movement, touch, taste, smell, vision, and hearing to put them together with prior information, memories, and knowledge stored in the brain to make a meaningful and appropriate response to one's environment.
Disorders of the vestibular system in individuals has been linked to a number of developmental disorders. Studies have shown that stimulating the vestibular system of subjects has resulted in improved motor control, social behavior, and balance. Chee et al. (Phys Ther. 1978 September; 58(9):1071-5) observed improved reflex and gross motor skills. Vestibular stimulation has also been used to treat developmentally delayed subjects. MacLean and Baumeister (J Abnorm Child Psychol. 1982 June; 10(2):229-45) provided vestibular stimulation to developmentally delayed babies by rotating the children in a motor-driven chair at a constant velocity. The acceleration was not measured. Ottenbacher (1: Phys Ther. 1983 March; 63(3):338-42) used vestibular stimulation to improve neuromotor development in high-risk infants and developmentally delayed children. Magrun et al. (Am J Occup Ther. 1981 February; 35(2):101-4) showed an increase in spontaneous verbal language use for primary trainable mentally deficient and developmentally retarded preschoolers immediately after the stimulation periods. Uyanik et al. (Pediatrics International Volume 45 Issue 1 Page 68-February 2003) tested vestibular stimulation on children with Down syndrome. Sensory integration, vestibular stimulation and neurodevelopmental therapy were effective in children with Down syndrome. Ray et al. (THE OCCUPATIONAL THERAPY JOURNAL OF RESEARCH 83, pg. 187-191) showed the effect of vestibular stimulation resulted in an increased percentage of vocalizations when an autistic child used a swing for vestibular stimulation. Slavik et al. (Neuropediatrics. 1984 February; 15(1):33-6) showed increased duration of eye contact for autistic boys on hand-operated oscillating swing.
Most protocols for applying vestibular stimulation only applied an angular acceleration at the very beginning and end of the profile, for a total of approximately four seconds. For example, when a subject is accelerated to a constant velocity, the only acceleration felt by the subject occurs during acceleration and deceleration. Subjects thus were accelerated to a constant velocity. After acceleration to a constant velocity, the stimulus to the semi-circular canals dampens; in fact, in the absence of visual input, the subject will no longer feel they are spinning. Further, previous methods of applying vestibular stimulation are not measurable, repeatable, or conducive to applying different patterns in different directions.
There is therefore a need for systems designed to apply accelerations and decelerations in reproducible and repeatable fashion. This and other needs are addressed by the present invention.